Electric switch



Oct. 27, 1925- H. TRENCHAM ELECTRIC SWITCH Filed Nov. 6. 1923 2 Sheets-Sheet" 1.

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H. TRENCHAM ELECTRIC SWITCH Filed Nov. 6. 1923 2 Sheets-Sheet 2 lnvehbor-z Henr'x Trencham:

His Abner-he' Patented a. 27, 1925.

UNITED STATES PATENT OFFICE.

' HENRY TRENCHAM, OF RUISIIIP, ENGLAND, ASSIGNOR T0 GENERAL ELECTRIC COM- PANY, A CORPORATION OF NEW YORK.

ELECTRIC SWITCH.

Application filed November 6, 1923. Serial m). 673,089.

To all whom it may concern:

Be it knownthat I, HENRY TRENCHAM, a British subject, residing at Ruisli inthe county of Middlesex, England, ave inl vented certain new and useful Improvements in Electric Switches, of which the following is a specification.

My invention relates to high tension electric switches of the enclosed type in which 10 the live parts are immersed in an insulating liquid such as oil. After such switches have \been in use for some time moisture and other impurities in the oil may have lowered the insulation resistance to such an extent that leakage from the live contacts to contacts supposedly dead may be sufiicient to render dangerous the handling of the latter contacts or of any circuit connected therewith.

An object of my invention therefore is to 90 provide a switch construction of the type in which both contracts are always immersed in the insulating liquid such that the above noted danger is avoided. This object I accomplish by providing one or more grounded 25 screens in the liquid comprising portions arranged to be moved between the live parts and th other parts of the switch apparatus whenever the switch is moved to open position.

80 My invention will be better understood by reference to the accompanying specification and drawing and its scope will be pointed out in the appended claims.

In the drawing, Figure 1 is a side eleva tion partly in section ofa knife switch embodying my invention; Fig. 2 is a fragmentary cross sectional view taken on the line 22 of Fig. 1; Fi 3 is a side elevation partly in section 0 a double break switch in w ichthe contacts at both breaks are provided with grounded screens;v Fig. 4 is a cross sectional viewv taken on the line 44 of Fig. 3; Fig. 5 is a side elevation partly in section of a difi'erent form of double break 45 switch with which a single grounded screen is used; and Fig. 6 is a plan view of the switch shown in Fig. 5.

Referring first to Figs. 1 and 2, the contact studs 1 and 2 of the switch are secured to the plate 3 of the frame of the switch gear by the insulating bushings 4. The movable contact member, consisting in this case of the laminated knife blade 5, is pivoted to the stud 2 at 6 and is actuated by a rod 7.

This rod is divided into two sections separated by an insulating portion 8 and at its upper end connects with arm 9 of a threearmed lever which lever is pivotally mounted on the lug 10 depending from the to plate or frame 11 of the switch gear. od 12 connects'with'another arm 13 of the lever and by it the openingand closing movements of the switch blade are eifected. The third arm 14 of the lever connects by an inclined rod 15 through a link 16 with a bell crank 17 fulcrumed on a bracket 18 extending from the casing 19. The casing 19 is secured to the plate 3, through which it is grounded, and partly encloses the contact terminal 1 having its upper portion cut away to form an opening 20 and within the casing 19 slides a shutter 21 adapted when shifted to the left in Fig. 2 to close the openmg therein. Connection is made between the shutter 21 and the bell crank 17 by means of a rod 22 having a pin and slot connection with the lever as shown.

The operation of the apparatus thus described is as follows: With the switch closed as shown in full lines in Figs. 1 and 2, the shutter 21 occupies a position at the right hand end of the casing 19. When the rod 12 is pulled to rock the three-armed lever the switch is moved by rod 7 to its open circuit position, indicated by dotted lines on the.

drawing. At the same time, the rod 15 is moved downwardly rocking the bell crank 17 and shifting the shutter 21 to the left so that when the switch arm has reached its full open position the shutter closes the opening in the casing; In closing the switch the shutter is moved to the right as the switch blade is rocked to engage the stationary contact. The switch blade and the shutter are so related that in their movements they cannot contact with each other.

In the form of my invention illustrated by Fig. 3 the two stationary contacts 25, supported by the insulating bushings 26, are adapted to be connected by member 27 to close the circuit. This bridging member is moved vertically by actuating rod 28 which has an insulation section as in the previous form. Rod 28 carries the arm 29 having the pin 30 which slides in the slot 31 in the u per end of the rod 32. The lower end of rod 32 is pivotally connected to the arcuate shutter 34 which has parallel side the bridging faces by which it is pivotally secured to the cylindrical casing 36 surrounding one of the bushings 26. The other bushing has a similar casing 37 and shutter 38, the two shutters being connected together to operate in unison by a link 39. Each shutter is of a suflicient width to completely close the open end of its respective casing when moved to the dotted line position corresponding to the open circuit position of the bridging memher. In opening the switchaccording to this form of the invention, the rod 28 and bridging member 27 move upward until the pin 30 reaches the end of the slot 31 when further movement thereof raises the rod 32, also thus rocking the shutters 34 and to close the openings over the stationary contacts. The provision of the pin and slot connection between the arm 29 and the rod 32 insures that in opening the switch the movable contacts shall be clear of the open ends of the casings before the latter are covered by the shutters. In closing the switch the weight of the shutters and the rods 32 may be suflicient to move the shut ters to open position.

In the form of my invention illustrated by Figs. 5 and 6 the two insulating bush-' ings 40 and 41 supporting the stationary contacts are arranged in alinement with the bridging member 42 arranged to be moved vertically between them by the operating rod 43. The bushing 40 is partly enclosed by the square or rectangular casing 44 provided with an opening 45. The cooperating shutter 47 secured to the rod 48 pivotally mounted in brackets 49 is adapted to be swung from a position shown in full lines in Fig. 6 tothe dotted line position whereby it covers the opening in the casing 44. The rod 48 carries at its upper end a member 50 having a cam slot 51 the lower portion of which, for example, the lower twothirds is vertical while the upper portion is helical, as shown, making a ninety degree turn. The arm 53 secured to the rod 13 has its free end engaging in the slot 51 whereby vertical movement of the rod 43 to the dotted line position produces a rotative movement of the shutter carrying rod 48. Thus it will be seen that as the rod 43 is raised to open the switch the arm will first travel through the vertical portion of the cam slot but upon reaching the helical portion of the slot will turn the shutter to such a position that it will close the opening in the casin Movement of the rod 43 in the opposite d1- motion from the dotted line position first causes the shutter to swing away from the casing leaving the openin therein free for the entrance of the mova le contact.

The switches illustrated in the foregoing examples are suitable as isolation switches and as so used the contact which is rovided with the shutter would be connecte directly connect with the oil circuit breaker.

to a bus'bar while the other contact would Should the oil circuit breaker or other apparatus have to be handled or removed for inspection purposes, or should the circuit connected therewith, require attention, the circuit is first broken in the ordinary way and then the isolation switch is opened. It is essential that in the position of'the switch gear no current shall leak through the oil surrounding the isolation contacts from the live contact, While parts, which are sup posed to be dead after the opening of the switch, are being handled. By so coverin the live isolation contact with a grounde screen any current leakin from the contact will be conducted directy to ground and consequently those parts which are supposed to be dead can be handled with perfect safety. It will be understood that while the screens are shown as grounded through their connection with the plate or frame supporting the insulating bushings, separate grounding leads may be used for this purpose if desired.

Obviously the invention can equally be applied to an oil circuit breaker itself, the live In case of three-phase or other circuits, I i

may use a single grounded screen in connection with the several terminals, or a single actuating rod to actuate several separate switches and screens on their respective compartments.

While I have described several embodinnents of my invention, I do not wish to be limited to the particular forms shown and described as it will be apparent that many other modifications therein may be made without departing from the scope of my invention as set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is,-

1. Electric switch gear of the ty having the live parts immersed in an insu ating liquid characterized by the fact that a grounded screen is provided within the liquid between the live-parts and other parts of the gear when it is desired to render the latter dead and free fromleakage currents.

2. In a fluid break switch, a stationary contact, a movable contact, and protective I grounding means comprismg a casing surenclose said stationary contact when said switch is open.

3. In a fluid break switch, a stationary contact, a cooperating movable contact, a grounded casing partially enclosing said stationary contact, a shutter pivoted to said casing, and interconnectedimeans for moving said movable contact to open circuit position and for rocking said shutter to a position to completely enclose said station- 10 ary contact in cooperation with said casing. In witness whereof,- I have hereunto set my hand this 26th day of October, 1923. HENRY TRENCHAM. 

